Medical lead with tissue-protecting tip structure

Abstract

A transvenous cardiac lead comprises a lead body having a distal end portion comprising a tip adapted to be placed in engagement with cardiac tissue. A protective device is carried by the distal end portion of the lead body in operative association with the tip, the protective device being deployable following placement of the tip to protect the cardiac tissue engaged by the tip. The deployable protective device may be expandable upon implantation to provide a larger surface area or footprint about the lead tip so as to retard or reduce the risk of penetration or perforation of the myocardium by the tip. The protective device may comprise a matrix expandable in response to contact with bodily fluids. Preferably, the expandable matrix comprises hydrogel. Alternatively, the protective device may comprise at least one electroactive polymer element electrically connected to a proximal end of the lead body.

1 . A transvenous cardiac lead comprising: 
 a lead body having a distal end portion comprising a tip adapted to be placed in engagement with cardiac tissue; and 
 a protective device carried by the distal end portion of the lead body, the protective device being deployable following placement of the tip to protect the cardiac tissue engaged by the tip against the potential for the lead body tip to perforate or penetrate the cardiac tissue.  
   
   
   
       2 . The lead of  claim 1  wherein: 
 said protective device comprises a matrix expandable in response to contact with bodily fluids.    
   
   
       3 . The lead of  claim 2  wherein: 
 the expandable matrix expands at least 30% when contacted by bodily fluids.    
   
   
       4 . The lead of  claim 2  wherein: 
 said expandable matrix carries a material selected from the group consisting of an electrolyte, a drug, a radiopaque substance and an echographic substance.    
   
   
       5 . The lead of  claim 2  wherein: 
 the expandable matrix comprises hydrogel.    
   
   
       6 . The lead of  claim 1  wherein: 
 the protective device comprises at least one electroactive polymer element electrically connected to a proximal end of the lead body.    
   
   
       7 . The lead of  claim 1  wherein: 
 said tip comprises a tip electrode.    
   
   
       8 . The lead of  claim 1  wherein: 
 said tip comprises a helical screw-in element.    
   
   
       9 . The lead of  claim 8  wherein: 
 said protective device is carried by said helical screw-in element.    
   
   
       10 . A transvenously implantable cardiac lead comprising: 
 a lead body having an outer surface, a distal end portion, and a proximal end carrying at least one electrical contact connected to a tip electrode adapted to be placed in engagement with cardiac tissue upon implantation; and    a protective device carried by the outer surface of the lead body proximal of the tip electrode, said protective device being deployable after implantation to protect the cardiac tissue engaged by the tip electrode.    
   
   
       11 . The lead of  claim 10  wherein: 
 said protective device comprises a matrix expandable in response to contact with bodily fluids.    
   
   
       12 . The lead of  claim 10  wherein: 
 said expandable matrix carries a material selected from the group consisting of an electrolyte, a drug, a radiopaque substance and an echographic substance.    
   
   
       13 . The lead of  claim 10  wherein: 
 the protective device comprises a layer of hydrogel, said layer being expandable after implantation as a result of contact with bodily fluid.    
   
   
       14 . The lead of  claim 13  wherein: 
 said hydrogel is blended with a non-hydrogel polymer.    
   
   
       15 . The lead of  claim 10  wherein: 
 said protective device comprises at least one electroactive polymer element electrically connected to the proximal end of the lead, said at least one electroactive polymer element having a normally deployed state in the absence of an electrical signal and a non-deployed state in response to the application of an electrical signal to the at least one electroactive polymer element.    
   
   
       16 . The lead of  claim 15  wherein: 
 the at least one electroactive polymer element is attached to the outer surface of the lead body along a distal edge of the element.    
   
   
       17 . A transvenous cardiac lead comprising: 
 a lead body having a distal end portion comprising a tip adapted to be placed in engagement with cardiac tissue; and 
 a protective device carried by the distal end portion of the lead body, the protective device being radially expandable to assume an expanded state following placement of the tip.